linux-kernel - Re: [PATCH] mm: don't be stuck to rmap lock on reclaim path

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Date:   Tue, 17 May 2022 16:58:54 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        John Dias <joaodias@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: Re: [PATCH] mm: don't be stuck to rmap lock on reclaim path

On Wed, 4 May 2022 23:11:04 -0700 Minchan Kim <minchan@...nel.org> wrote:

> > > +
> > > +	static struct rmap_walk_control rwc = {
> > >  		.rmap_one = page_idle_clear_pte_refs_one,
> > >  		.anon_lock = folio_lock_anon_vma_read,
> > >  	};
> 
> So, delta is

--- a/mm/page_idle.c~mm-dont-be-stuck-to-rmap-lock-on-reclaim-path-fix
+++ a/mm/page_idle.c
@@ -87,6 +87,10 @@ static void page_idle_clear_pte_refs(str
 {
 	struct folio *folio = page_folio(page);
 
+	/*
+	 * Since rwc.try_lock is unused, rwc is effectively immutable, so we
+	 * can make it static to save some cycles and stack.
+	 */
 	static struct rmap_walk_control rwc = {
 		.rmap_one = page_idle_clear_pte_refs_one,
 		.anon_lock = folio_lock_anon_vma_read,
_

and with that, I believe this change is good to be imported into mm-stable
later this week.